What is "kbps"?
A number of messages on the website are now available in both "16kbps" and "32kbps" versions, but what does this mean?
Basically, it refers to the quality of sound. The higher the "kbps", the more realistic the audio will be.
"Kbps" stands for kilo-bits per second. "Kilo" means "thousand," so "16kbps" means "16 thousand bits per second," and "32kbps" means "32 thousand bits per second."
One way to explain what this means with respect to audio quality, is to use a "connect-the-dots" picture as an illustration. Most of us have made connect-the-dots pictures as children. Basically you have an original image, and a certain number of dots are used to help reproduce that image. The child draws straight lines from dot number "1" to dot number "2", etc., until they are all complete. Eventually, instead of having a page full of incomprehensible dots, an image will begin to appear. The more dots that are used, the more accurate the resulting picture will look. For example if you start with a perfect circle as your original image, but only use 5 dots, the resulting image will be a pentagon. If however you doubled the "dot-rate" and used 10, spreading them out evenly around the circumference of the circle, the image will be twice as accurate in reproducing the original circle as was the 5-dot version. Suppose now that you used 16 thousand dots. Then think about 32,000 dots, etc., etc. Get the idea? The resulting images will get closer and closer to the original, the more dots one uses.
Another illustration might be that of a motion picture. Early films usually look quite jumpy because the "dot-rates" of the cameras were relatively low. The more photos the camera can take per second, the more life-like the movie will be when it is played back.
When digitally capturing an audio message with a computer, the software can be set to take 16,000 "photos" or "dots" per second, 32,000 "bits" per second, or 64,000, etc., depending on how accurate one wants the resulting audio to be. When the computer plays back these files, it is basically "connecting-the-dots" in an attempt to reproduce the original audio vibrations. These signals are then amplified sufficiently to move your speakers, which in turn produce vibrations in the air that correspond to the original speaker's voice.
Since a human voice has a very limited frequency range, a "16kbps" file can do a reasonably good job of reproducing a sermon. This bit rate is very common on many websites which specialize in producing audio files for voice. Many of the (now) older-format "Real Audio" files for voice were 16kbps. This bitrate would not be very good for reproducing say a Beethoven symphony however — at least with a decent degree of life-likeness — since the frequencies produced by an orchestra are much broader. However, 16kbps is generally acceptable with most people for sermon reproduction. A 16kbps sermon is just as edifying as a 32kbps version, because the words can be readily understood in both formats. The 16kbps rate helps keep the MP3 files relatively small. Whenever the bitrate is doubled, it basically doubles the size of the files. This is especially important considering that not everybody in the world has high-speed DSL or FIOS: some places still have dial-up access to the internet, so sizes need to be small enough for these folks to download them in a reasonable amount of time. This is especially critical when a long series needs to be downloaded.
All this being said however, since faster internet speeds are quickly becoming more and more the norm, higher-quality audio files are also becoming more and more reasonable — even for a long series which can have dozens or even hundreds of messages. The higher bitrate messages do produce a more life-like sound quality, and thus can give more of a sense of "being there."
Whether you should choose 16kbps or 32kbps is totally up to you then — depending on if & how fast you might want to download files, how much you are concerned about audio quality, the amount of space you might have for storing the files, data-rates, etc. To get a sense of the quality difference you could try a particular sermon in both formats & compare them.
If only one file is on the site it generally means it is 16kbps. The on-site embedded players will use the highest quality that is available.